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LHCb Collaboration(Aaij, R. et al), Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., & Ruiz Vidal, J. (2022). Observation of two new excited Ξ0b states decaying to Λ0bK−π+. Phys. Rev. Lett., 128(16), 162001–12pp.
Abstract: Two narrow resonant states are observed in the Λ0bK−π+ mass spectrum using a data sample of proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the LHCb experiment and corresponding to an integrated luminosity of 6 fb−1. The minimal quark content of the Λ0bK−π+ system indicates that these are excited Ξ0b baryons. The masses of the Ξb(6327)0 and Ξb(6333)0 states are m(Ξb(6327)0)=6327.28+0.23−0.21±0.12±0.24 MeV and m(Ξb(6333)0)=6332.69+0.17−0.18±0.03±0.22 MeV, respectively, with a mass splitting of Δm=5.41+0.26−0.27±0.12 MeV, where the uncertainties are statistical, systematic and due to the Λ0b mass measurement. The measured natural widths of these states are consistent with zero, with upper limits of Γ(Ξb(6327)0)<2.20 (2.56) MeV and Γ(Ξb(6333)0)<1.60 (1.92) MeV at a 90% (95%) credibility level. The significance of the two-peak hypothesis is larger than nine (five) Gaussian standard deviations compared to the no-peak (one-peak) hypothesis. The masses, widths and resonant structure of the new states are in good agreement with the expectations for a doublet of 1D Ξ0b resonances.
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Garcia Soto, A., Zhelnin, P., Safa, I., & Arguelles, C. A. (2022). Tau Appearance from High-Energy Neutrino Interactions. Phys. Rev. Lett., 128(17), 171101–7pp.
Abstract: High-energy muon and electron neutrinos yield a non-negligible flux of tau neutrinos as they propagate through Earth. In this Letter, we address the impact of this additional component in the PeV and EeV energy regimes for the first time. Above 300 TeV, this contribution is predicted to be significantly larger than the atmospheric background, and it alters current and future neutrino telescopes' capabilities to discover a cosmic tau-neutrino flux. Further, we demonstrate that Earth-skimming neutrino experiments, designed to observe tau neutrinos, will be sensitive to cosmogenic neutrinos even in extreme scenarios without a primary tau-neutrino component.
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Phong, V. H. et al, Agramunt, J., Algora, A., Domingo-Pardo, C., Morales, A. I., Rubio, B., et al. (2022). Beta-Delayed One and Two Neutron Emission Probabilities South-East of Sn-132 and the Odd-Even Systematics in r-Process Nuclide Abundances. Phys. Rev. Lett., 129(18), 172701–7pp.
Abstract: The beta-delayed one- and two-neutron emission probabilities (P-1n and P-2n) of 20 neutron-rich nuclei with N >= 82 have been measured at the RIBF facility of the RIKEN Nishina Center. P-1n of Ag-130;131, Cd-133;134, In-135;136, and (138;13)9Sn were determined for the first time, and stringent upper limits were placed on P-2n for nearly all cases. beta-delayed two-neutron emission (beta 2n) was unambiguously identified in Cd-133 and In-135;136, and their P-2n were measured. Weak beta 2n was also detected from Sn-137;138. Our results highlight the effect of the N = 82 and Z = 50 shell closures on beta-delayed neutron emission probability and provide stringent benchmarks for newly developed macroscopic-microscopic and self-consistent global models with the inclusion of a statistical treatment of neutron and. emission. The impact of our measurements on r-process nucleosynthesis was studied in a neutron star merger scenario. Our P-1n and P-2n have a direct impact on the
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LHCb Collaboration(Aaij, R. et al), Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., & Ruiz Vidal, J. (2022). Tests of Lepton Universality Using B-0 -> K(S)(0)l(+) l(-) and B+ -> K*(+)l(+)l(-) Decays. Phys. Rev. Lett., 128(19), 191802–15pp.
Abstract: Tests of lepton universality in B-0 -> K(S)(0)l(+)l(-) and B+ -> K*(+)l(+)l(-) decays where l is either an electron or a muon are presented. The differential branching fractions of B-0 -> K(S)(0)e(+)e(-) and B+ -> K*(+)e(+)e(-) decays are measured in intervals of the dilepton invariant mass squared. The measurements are performed using proton-proton collision data recorded by the LHCb experiment, corresponding to an integrated luminosity of 9 fb(-1). The results are consistent with the standard model and previous tests of lepton universality in related decay modes. The first observation of B-0 -> K(S)(0)e(+)e(-) and B+ -> K*(+)e(+)e(-) decays is reported.
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LHCb Collaboration(Aaij, R. et al), Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., & Ruiz Vidal, J. (2022). Observation of the Decay Lambda(0)(b) -> Lambda(+)(c) tau(-)(nu)over-bar(tau). Phys. Rev. Lett., 128(19), 191803–11pp.
Abstract: The first observation of the semileptonic b-baryon decay Lambda(0)(b) -> Lambda(+)(c) tau(-)(nu) over bar (tau) with a significance of 6.1 sigma, is reported using a data sample corresponding to 3 fb(-1) of integrated luminosity, collected by the LHCb experiment at center-of-mass energies of 7 and 8 TeV at the LHC. The tau(-) lepton is reconstructed in the hadronic decay to three charged pions. The ratio K = B(Lambda(0)(b) -> Lambda(+)(c) tau(-)(nu) over bar (tau))/B(Lambda(0)(b) -> Lambda(+)(c)pi(-)pi(+)pi(-)) is measured to be 2.46 +/- 0.27 +/- 0.40, where the first uncertainty is statistical and the second systematic. The branching fraction B(Lambda(0)(b) -> Lambda(+)(c) tau(-)(nu) over bar (tau)) (1.50 +/- 0.16 +/- 0.25 +/- 0.23)% is obtained, where the third uncertainty is from the external branching fraction of the normalization channel Lambda(0)(b) -> Lambda(+)(c)pi(-)pi(+)pi(-). The ratio of semileptonic branching fractions R(Lambda(+)(c)) B(Lambda(0)(b) -> Lambda(+)(c) tau(-)(nu) over bar (tau))/B(Lambda(0)(b) -> Lambda(+)(c)mu(-)(nu) over bar (tau)) is derived to be 0.242 +/- 0.026 +/- 0.040 +/- 0.059, where the external branching fraction uncertainty from the channel Lambda(0)(b) -> Lambda(+)(c)mu(-)(nu) over bar (tau) contributes to the last term. This result is in agreement with the standard model prediction.
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